1. Field of the Invention
The present invention relates to a method used in a communication system and related communication device, and more particularly, to a method of performing a Service Group Discovery procedure in a communication system and related communication device.
2. Description of the Prior Art
The Open Mobile Alliance (OMA) is founded to develop OMA specifications for mobile services to meet users' needs. Furthermore, the OMA specifications aim to provide the mobile services which are interoperable across geographic areas (e.g. countries), operators, service providers, networks, operation systems and mobile devices. In detail, the mobile services conforming to the OMA specifications can be used by the users without restriction to particular operators and service providers. The mobile services conforming to the OMA specifications are also bearer agnostic, i.e., the bearer that carries the mobile services can be a second generation (2G) mobile system such as GSM, EDGE or GPRS, or a third generation (3G) and beyond mobile system such as UMTS, LTE or LTE-Advanced. Further, the mobile services can be executed on an operation system such as Windows, Android or Linux operated on various mobile devices. Therefore, industries providing devices or the mobile services supporting the OMA specifications can benefit from a largely growing market enabled by interoperability of the mobile services. Besides, the users use the devices or the mobile services supporting the OMA specifications can also have a better experience due to the interoperability of the mobile services.
Furthermore, Converged Personal Network Services (CPNS) is developed by the OMA to provide application-layer support for ubiquitous access to services in a converged network, which is a group of Personal Networks (PNs) that are interconnected by PN Gateways (PN GWs). In detail, a basic architecture of the CPNS includes three entities which are a CPNS server, a PN GW, and one or more PN elements (PNEs), but there may be several PNGWs, or even several CPNS servers, or even service provider servers in other architectures of the CPNS. The CPNS server receives requests from the PN GW, and replies responses to the PN GW, to ensure that appropriate applications are selected and appropriate contents are provided to the PNEs via the PN GW. The PN GW serves as an intermediary entity between the PNEs and other networks that forwards the requests and the responses between the PNEs and the other networks. The PNEs are PN entities that are connected to the PN GW and between each other and are used for rendering the content received from the PN GW or from each other. The PNE can be a mobile phone, a personal computer (PC), a music player, a car navigation system or an IP-enabled set-top box.
On the other hand, the OMA develops a concept of service group (SG) for the CPNS. The SG is composed of a CPNS server, one or more PN GWs and one or more PNEs. The intention of the service group is to group together PNEs which want to receive the same service from a CPNS server or a content provider. In other words, for those PNEs that want to receive a game service can belong to a SG receiving the game service, and for those PNEs that want to receive a music service can belong to a SG receiving the music service.
Based on the CPNS protocol specification, creation of a SG is initiated by a PNE. Under such a situation, a Service Group Discovery procedure, i.e. Service Group Query procedure, is performed for the PNE to know the existence of other SGs, such that the Service Group Discovery procedure can be executed to avoid certain circumstances of redundant SG creation, e.g. existing SGs available to provide the service the PNE wants to consume, and also can be applied when the PNE tries to join other SGs. However, detailed content and format of messages of the Service Group Discovery procedure is not yet specified.